Piston



' Aug. 26, 1941.

R. G. BERRY PISTON Filed Aug. 4, Y1938 Patented Aug. 26, 1941 I UNITED STATES PATENT OFFICE rrs'roN Russell G. Berry, Maplewood, Mo., assignor to Carter Carburetor'` Corporation, St. Louis, Mo., Aa corporation of Delaware Application August 4, 193s, serlsrNo. 222,979

. u (Cl.` 309-7) This invention relates toA pistons particularly 4 Claims.

of the type used in pumps. l

Pump pistons, such as those vused in automotive carburetors for providing an extra accelerating charge,- are frequently provided with cup-shaped sealing leathers having disc-shaped end walls and cylindrical skirt portions intersecting in a corner of small radius. The leather skirt is yieldingly urged against the pump cylinder wall to form a piston seal and during reciprocation of the piston, particularly, in the direction towards which the concave face of the piston leather faces, a slight crimping occurs at the corner which, after repeated operation, weakens the leather and frequently results in cracks. The leather cup vmay be formed in a circular die which process results in weakened corner structure, further aggravating the difliculty.

An object of the present invention is to provide a pump sealing leather which is substantially more resistant to failure due to crimping,

as described above, than pump leathers hereto.

fore known.

A more detailed object is to provide a pump sealing leather without a relatively sharp corner at the intersection of the skirt and end wall portions thereof. Still another object is to provide A a pump sealing leather adapted to be formed in a die without weakening of restricted portions thereof, such as occurs in die-formed cupshaped leathers. Y

These objects and other more detailed objects hereafter appearing are attained substantially by the 'structure .illustrated in the accompanying drawing in which:

Fig. 1 is a side View and section of an auto.- motive carburetor including an accelerating pump embodying the invention.

Fig. 2 is a perspective view illustrating the pump piston, a part being broken away and sectionedfor clearer illustration of the underlying Structure.

- Fig. 3 is a section taken approximately on line 3-3 of Fig. 2 and v Fig. 4 is a( side view showing an old form of pump piston, a part being broken away and sectioned for clearer illustration.

The carburetor shown in Fig. 1 includes a constant level chamber 5 and downdraftmixture barrel 6 flanged at the lower end as at 1 for attachment to 'the intake manifold (not shown) of -an associated internal combustion engine. The fuel level in chamber 5 is maintained substantially constant by inlet needle valve 8 conrel from chamber 5 through a calibrated orifice member I0 controlled'by metering rod II carried by lever I2 pivoted above the constant level chamber. ing purposes is supplied by a pump including cylinder I 3 inside the constant level chamber and a piston, generally indicated at I 4, and operated from the throttle valve through the intermediary of lever I2, link I5, and crank I6 secured to the throttle valve shaft I1.

The pump piston, more clearly shown in Figs. 2 andA 3, comprises a rigid body or inner clamping portion including a dome-shaped upper part I8 and a 'cylindrical lower part I9 forming a dome for trapping cushioning air. Between parts I8 and I9 is a groove 20 in which is received an annular coiled spring 2|. Piston rod 22 is rigid with part I8 and projects from the center thereof.

4The pump sealing or packing washer, preferably of leather, includes a dome-shaped or hemispherical transverse or end wall 23 seated against the transverse surface of part I8 around rod 22 and a cylindrical section 24 forming a skirt for'initially engaging the pump cylinder wall and yieldingly urged thereagainst by spring 2|. A curved washer 2'5 is seated against shoulder 26 on piston rod 22 and has an inner surface shaped as a spherical sector forming a reinforcing backing for the pump leather.

r Washer 25 is substantially smaller in diameter than the cylinder I3 which allows a substantial portion of the sealing leather to ex as the direction of motion is changed. Rod 22 is .threadedl at its lower end and provided with a nut 2'I and Washer 28 for maintaining the assembly.

Fig. 4 shows a pump piston having a chamber sealing leather of known shape including cylin-4 drical skirt 32 and disc-shaped end wall 29. A

spring 30 urges the skirt outwardly. The skirt and end wall meet in a relatively sharp corner 3l. By comparison with Fig. 4, it will be seen that the novel leather sealing member in Fig. 2 has no sharp corner as at 3I` in Fig. 4 which causes stress concentration during the pressure lstroke. In addition to eliminating the sharp corner which tends to weaken after-.repeated reciprocations, due to crimping, the dome-shaped leather in Fig. 2 is shaped so that strains produced therein during formation in a die are equally distributed over the body of the leather.

The novel pump leather'may be formed hemispherical. or dome-shaped in its entirety, or provided with a short, cylindrical section4 at its lowergopen end for rubbing against the pump troneo by neat s. Fuelreacnesthe mixmre bar-55 cylinder wan. Use a the piston in an alc.

An extra supply of fuel for accelerathalf the diameter of said head end cylindrical portion.

2; For use in a pump of the class described having a pump cylinder, a one-piece piston having a substantial portion of its length extending from its head end of cylindrical form and adapted to slidably t the pump cylinder and having its opposite end of hemispherical form and of substantially smaller diameter than said cylindrical portion and having an annular recess intermediate said cylindrical portion and said hemispherical end.

3. A piston as described in claim 2 which is further characterized by a longitudinal central bore therethrough and a counterbore at the head end thereof.

4. For use in a pump of the class described having a pump cylinder, a piston formed of Va,

single ,piece of material having a substantial portion of its length extending from its head end of cylindrical `form and adapted to slidably iit the pump cylinder, and having its opposite end of hemispherical form and of substantially smaller diameter than said cylindrical portion and having an annular recess intermediate said cylindrical portion and said hemispherical end, and a cup-shaped resilient packing member having a hemispherical closed end adapted to iit over the hemispherical end of said piston and having a skirt long enough to extend beyond said annular recess.

RUSSEL G. BERRY. 

